Process of degumming silk



UNITED 1,644,764 orsice.

LEO WALLERS'I'EIN, OF NEW YORK, N. Y ASSIGNOR TO WAILERSTEIN OOMIANY, INC.

I OF NEW YORK, N. Y., A CORPORATION OF NEW YORK. i

PROCESS OF DEGUMMING SILK.

E Drawing. Application filed April 15, 1922, Serial No. 558,279. Renewed February 24, 1928.

This invention relates to a process for degumming silk.

The object of the invention is to provide a process which will-be more economical than the proceszes heretofore known and which may be carried out in pract ce with ordinary care without danger of 1njury to the silk.

With this general object in view, the in- Jo vention broadly considered. comprises a treatment of the silk with a solution of a proteolytic enzyme which is active in an acid, in a slightly alkaline, and in a neutral medium. While there are a number of such proteolytic enzymes which may be used, the proteolytic enzyme known in commerce as papain is especially suitable for the purposes of this invention.

I now ive some specific example of the manner 05 carrying out my invention.

The raw silk ma be subjected first to the action of a wea soap solution, as, for example, a solution containing 4% soap. While the amount of such solution relative to the amount of raw silk may vary and need only be such as to permit the convenient washing and working of the silk, it is-advisable to so proportion the baththat the ='-total soap therein will be about 2 to 5 per cent of the weight of the raw silk to be treated. This bath is kept at a temperature of 70 to 95 'C., and the raw silk is allowed to remain in the bath for about 5 to 15 minutes. This bath is a rinsing bath for the purpose of removin any surface dirt, oils, andimpurities. .t' the end of this treatment the silk is removed and the water pressed out in any suitable manner, as, for example, by a wringer or a centri- 40 fuge.

Instead of this soap solution some other weakly alkaline solution may be employed, as, for example, a weak solution of sodium carbonate or bicarbonate.

The silk is then immersed in a very wea solution of papain. This solution is made in the proportion of 1 gm. of papain to 4 to 5 liters of water. When the silk is first immersed, the bath should be at a temperature of about 50 to 7 0C., but the temperature is best raised to about 75 C. after the silk has been in the bath for a few minutes. The bath' is stirred at frequent intervals and the silk is worked over in the usual way so as to make sure thatthe solution comes into intimate contact with all parts of the silk. The. silk is kept in this for about one to two hours, at the end of which time it is removed to a rinsing bath of clean water, thoroughly rinsed and then dried. Instead of rinsing in clean water, the silk may be rinsed in a weak soap solution and then dried.

By the use of this treatment, viz, rinsing in a soap solution, the lustre and feel of the silk are inhanced. If the silk is to be dyed at once, it may be rinsed in the clean water or soap bath after removal from the papain solution, as described above, and then may go directly to the dyeing bath, which may contain some soap.

I have given the proportions of the papain solution as-l gm. of papain to 4 to 5 liters of Water and the time of treatment .as about one to two hours, but this is based on the assumption that the papain is of the normal commercial strength or activity. It is to be understood that variations in the proportions and in the'time of treatment may be necessary where the papain varies from the normal standard. The proportion of papain used depends on its activity and on its time of action, as well as on the condition of the silk.

In another example of the process, the degumming bath itself may contain soap. Forexample, papain may be added toa per cent soap solution in the proportion of 1 gm. to 4 to'5 liters'of soap solution. Infthis bath the silk is immersed and allowed to stay for 1 to 3 hours, the bath being kept at a temperature of about 50"- 0. when the silk is first immersed therein and may then be graduallyraised to 75 O. The silk may be worked over, in, the usual way, and when suiiiciently de mined may be moved to a rinsing bath 0 clean water,

rinsed, removed and dried. Or it may be given a treatment in another weak soap bath.

Also,.it may be advantageous to add to the water solution of papain a weak organic acid, for example, acetic acid, so that the resulting bath is slightly acid to litmus. The treatment of the silk in this bath is followed by a treatment in a weak soap solution. The use of the slightly acid papain hath tends to make the fibre tougher.

Instead of limiting the temperature of the papain and soap bath to 50 to 75 C., as stated above, it is sometimes advantageous to quickly raise the bath to 95 C. for a short time prior to removal of the silk to the rinsing bath.

By using a proteolytic enzyme which is active in all three classes of media, viz, acid, neutral and slightly alkaline, there is no danger of the enzyme action being stopped by changes in the degree of acidity or, alkalinity of the bath, such as might occur in practice, and also it becomes possible to use soap or acids with the enzyme in the bath, as hereinbefore pointed out.

What is claimed is. 1. The process of degumming silk, which comprises subjecting the silk to the action 'of a proteolytic enzyme of that type which is tion, and gradually increasing the temperature of the bath from about C. to about 7 5 C. l

3. The process of degumming silk, which comprises immersing it in a bath containing water and a proteolytic enzyme of that type which is active in a neutral as well as a weakly alkaline and a slightly acid solution, gradually increasing the temperature of the bath from about 50 C. to about 75 C., and then quickly raising the temperature to 95 C. for a short time before removing the silk from the bath.

. 4. The process of degumming silk which comprises immersing the silk in a bath containing water and a proteolytic enzyme of that type which is active in a neutral,- in a weakly alkaline and in a slightly acid solution, said bath being maintaine at a temperature not less than 50 C., allowing the silk to remain in the bath until sufiiciently degummed, and then removing the silk, rinsing and drying it. i

5. The process of degumming silk which comprises subjecting it to the action of a solution of papain at a temperature suflicient to maintain the activity of the enzyme, until the desired amount of degumming has occurred.

6. The process of degumming silk Which comprises subjecting it to an aqueous solution containing papain in the proportion of about 1 gm. of papain to 4 to 5liters of water, the bath being at about 50 to C. when the silk is entered,,gradually raising the temperature of the bath to about 0.,

and keeping the silk therein for about 1 hour.

7. The process of degummin silk which comprises first washing the si] in a soap solution then rinsing the silk, immersing it in a bath comprising an aqueous solution of a proteolytic enzyme of that type which is active in a neutral, in a weakly alkaline and in a slightly acid medium, maintaining the bath at a temperature of 50 to 75 C. until the silk is sufliciently degummed, and then removing the silk from the bath.

8. The process of degumming silk which comprises subjecting it to the action of a weak soap solution containing p-apain, while maintaining the solution at a temperature sufiicienfl to maintain the activity of the enzyme, until the desired amount of degumming has occurred.

9. The process of degumming silk which comprises subjecting it to the action of a solution containing papain and about to soap, while maintaining the solution at a temperature suflic'ient to maintain the activity of the enzyme, until the desired amount of degumming has occurred.

In testimony whereof, I have hereunto set my hand. a

LEO lVALLER STEIN. 

